Apparatus and method for non-intrusive assessment of gas in packages

ABSTRACT

A method and apparatus are disclosed for assessment of a sealed package. Light is emitted from a narrow-band laser source towards said package from outside of said package. An absorption signal of said light scattered in said package is measured, wherein said absorption is caused by said at least one gas when said light is scattered and travels in said sealed package. Measuring is made outside of said package, whereby said assessment is non-intrusive with regard to said package. It is determined if a deviation exists from a predetermined, expected gas composition and/or concentration of said at least one gas within said sealed package based on said measured absorption signal. Thus sealing of said package for said gas is detected.

RELATED APPLICATIONS

This application claims priority to International Patent Application No.PCT/EP2010/056511, International Filing Date 11 May 2010, entitledApparatus And Method For Non-Intrusive Assessment Of Gas In Packages,which claims priority to U.S. Provisional Application Ser. No.61/213,145 filed 11 May 2009 entitled Arrangement And Method ForNon-Intrusive Assessment Of Gas In Packages, both of which are herebyincorporated herein by reference in their entireties.

FIELD OF THE INVENTION

This invention pertains in general to the field of assessment ofpackages, and in particular of gas compositions in packages, such assealed packages including a gas volume. More precisely the inventionrelates to non-intrusive assessment of gas in food packages.

BACKGROUND OF THE INVENTION

In modern society, the trend among consumers to prefer fresh productsleads to that chilled food is more and more competing with frozen andambient counterparts. Fresh or chilled food is more sensitive, thusenhancing the demand from food consumers to be able to trust that thefood they buy and consume is safe. One important issue in the transferfrom ambient or frozen food products to chilled food is therefore theissue of safety and quality which is identified as an increasingconcern, emphasized frequently in industry and media.

The demand for fresh chilled food has created a need for distribution offresh products around the year. Fresh and chilled foods require bothquicker distribution due to shorter shelf life, and better product andpackage integrity due to safety and quality issues at the point ofconsumption. The two most important factors concerning the shelf lifeare time and temperature. Most of the deteriorating changes that takeplace in food are temperature dependent and occur at a slower rate atlower temperatures. In addition to the time and temperature parameters,the natural presence of oxygen in food products and packagingenvironments, hastens chemical breakdown and microbiological spoilage offood. Traditional packaging methods are therefore largely being replacedby newer techniques where other gases than oxygen are filled in thepackage headspace. Modified Atmosphere Packaging (MAP) is one example ofsuch techniques, used to reduce the oxygen content and to prolong theshelf life of the product it contains.

Due to food deteriorating aspects, the food handling, preservation andpackaging have become important aspects of great public interest andconcern. The MAP technology theoretically meets the new consumerrequirements of prolonged shelf-life for chilled or fresh products, andthe MAP packaging concept is growing in importance in the food packagingmarket. The main benefit of MAP is argued to be the reduction ofindirect costs due to less product waste. But with the increased qualityand safety concerns, the importance to be able to assess the status ofpacked food to ensure its quality and suitability for consumption mustalso be stressed. Many sensing techniques have been developed; however,most of them destroy the packaged sample and thereby cause waste of bothproducts and packages. E.g., gas chromatography and other samplingtechniques require puncturing the package for gas extraction, whilemeasurement techniques should preferably be non-intrusive in nature, inorder to maintain packaging integrity and reduce waste of samples.

Modified Atmosphere Packaging

Oxygen is a very reactive gas, naturally present in air. Most packagedfood items come with a natural headspace of air between the product andthe package. Oxygen is thus frequently present in the headspace. Due tothe high activity of this molecule, it is important to control itsconcentration in order to secure quality and increase shelf-life of theproduct. Generally, it is desirable to reduce its concentration fromambient (21 percent) to a few percent or to a completely oxygen-freeenvironment. By replacing the oxygen in the headspace the oxidativeprocesses are reduced and the shelf life of the food product isextended.

In order to reduce the natural concentration of oxygen in air, foodproducts are packaged in modified or controlled atmosphere. Modifiedatmosphere packaging (MAP), as used in this disclosure, is defined byHintlian and Hotchkiss as “the packaging of perishable product in anatmosphere which has been modified so that its composition is other thanair”. In MAP the natural oxygen content inside the package is replacedwith other gases such as carbon dioxide (CO2) or nitrogen (N2).Frequently, the gas composition is actively changed at the time ofpackaging, either by flowing gas during the packaging or by firstsubjecting the product to vacuum followed by inlet of the desired gasmixture.

Fresh products such as fruits or cured meat are the most common productsto pack in modified atmosphere. But more frequently, products such ashigh quality fruit juices are packed in modified atmosphere in order toreduce deterioration from oxidation and to extend the productshelf-life. The modified atmosphere is slowing chemical and biochemicaldeteriorative processes as well as slowing or preventing the growth ofspoilage organisms. For high quality fruit juices, nitrogen is the mostcommon gas to use in the headspace for replacement of oxygen. Nitrogenis an inert gas and does not dissolve well in water or lipids and thusensures that a package looks filled and is not collapsing. It has noanti-microbial activity but by displacing oxygen in the headspace ofpackages the oxidative processes of the products are delayed.

For MAP, the package integrity and tightness are necessary to maintainthe correct composition of gas inside the package, thus securing that nogas exchange takes place between the package and its environment. It isimportant to control the oxygen permeability in order to secure theprolonged shelf life of liquid food products, such as for example highquality orange juice. Packages with a modified atmosphere thereforerequire packaging materials that are tight to gas transfers, in order toavoid oxygen from getting into the headspace. For packages that have anexchange, (intended or not intended) with the outside environment,equilibrium will be reached between the inside and outside of thepackage over time with oxygen entering the headspace. Furthermore, in amodified atmosphere package, equilibrium of gas concentrations insidethe package may arise due to the interaction between the product and thegas contained in the package. A measurement method or apparatus isdesired for assessing the sealing tightness of the packaging. Suchmethod or apparatus is for instance suitable to detect the headspace gascomposition that will include the simultaneous gas movement frompermeation and through the exchange from product to headspace, in adynamic MAP system.

Non-Intrusive Gas Sensing of Food Packages

Measurement of oxygen contents in sealed packages might be the mostpertinent aspect of monitoring the gas composition in the headspace ofpackages. Oxygen assessment can be made by performing opticalmeasurements, using small sensor disks prepared to change in colour inthe presence of oxygen. Alternatively and more commonly used, the sensordisk is prepared with a ruthenium- or platinum-containing dye, withfluorescence properties that decreases with the amount of oxygen.However, these techniques are intrusive from the point of view that thesmall disks have to be introduced in the package at the time of sealing.In addition there is a cost and a safety aspect ensuring that the activereactive agent does not influence the product or the consumer. Hence, analternative non-intrusive method or apparatus would be advantageous.

From a safety and consumer perception aspect, non-intrusivemeasurements, without devices put on or inside the package are thereforecalled for. In addition all extra items incur an extra cost, in terms ofdirect costs and indirect costs such as extra handling time, machineinvestments etc. Non-intrusive measurements also allows for measurementsover time for packages during its entire shelf life.

SUMMARY OF THE INVENTION

Accordingly, embodiments of the present invention preferably seek tomitigate, alleviate or eliminate one or more deficiencies, disadvantagesor issues in the art, such as the above-identified, singly or in anycombination by providing a method and an apparatus according to theappended patent claims.

According to a first aspect of the invention a method is provided forassessment of a sealed package. The method comprises emitting light froma narrow-band laser source towards the package from outside of thepackage; measuring an absorption signal of the light scattered in thepackage, said absorption caused by at least one gas in said package whenthe light is scattered and travels in the sealed package. The measuringis made outside of the package, and the assessment is non-intrusive withregard to the package. The assessment is based on determining if adeviation exists from a predetermined, expected gas composition and/orconcentration of the at least one gas within the sealed package based onthe measured absorption signal.

According to a second aspect of the invention an apparatus is providedfor assessment of a sealed package. The apparatus comprises twonarrow-band laser sources adapted to emit light toward the package fromoutside of the package, and a light detector adapted to measureabsorption signal of the light scattered in the package. The absorptionis caused by the at least one gas when the light is scattered andtravels in the sealed package. The measuring is made outside of thepackage, and the assessment is non-intrusive with regard to the package.The apparatus further includes a control unit adapted to determine if adeviation exists from a predetermined, expected gas composition and/orconcentration of the at least one gas within the sealed package based onthe measured absorption signal.

Further embodiments of the invention are defined in the dependentclaims, wherein features for the second and subsequent aspects of theinvention are as for the first aspect mutatis mutandis.

Some embodiments provide for non-intrusive determining of a gasconcentration in a sealed package, and if a deviation exists from anexpected concentration or a deviation from a ratio between gasconcentrations or absorption signals. The ratio between the absorptionof an unknown gas with the absorption of a reference gas, e.g. watervapour, provides information about the measurement gas.

Some embodiments provide for remote assessment of a gas inside a sealedpackage.

Some embodiments provide for determining of the concentration of a gasin a sealed package which is translucent. To be able to use the methodthe package or sample need to be translucent, meaning that emitted lightmust be able to travel into the gas and interact with it and then outagain. The package can appear non-transparent to the naked eye, butlaser light might still be able to travel through it in a specifictranslucent wavelength window of the laser light. Embodiments providefor assessing information of gas inside packages, which are made of amaterial that is non-transparent, but translucent.

Some embodiments provide for assessment of gases inside sealed foodpackages having been sealed with modified atmosphere packaging (MAP),controlled atmosphere (CAP), or a unique composition of a gas.

Some embodiments provide for determining sealing tightness of a sealedpackage over time.

Some embodiments provide for determining if a sealed package has beensabotaged.

Some embodiments provide for determining if the product inside a sealedpackage is the product originally packaged in the sealed package.

Some embodiments provide for assessment of sealed packages in line witha product manufacturing chain devised for packaging of products in thesealed packages.

Some embodiments provide for assessment of sealed packages in a handheldcompact apparatus.

Gas absorption spectroscopy is an alternative gas sensing method forfood packages, interesting since it can provide non-intrusive, real-timemeasurements without the need to add sensors inside the packages. Thetechnique is based on the fact that each molecule absorbs light in aunique way, making them possible to identify and quantify withabsorption spectroscopy. A limitation of its conventional implementationis the need of a transparent package and headspace.

In 2001 an alternative approach of gas absorption spectroscopy, namedGASMAS (GAs in Scattering Media Absorption Spectroscopy) was presented,enabling sensing of gas surrounded by scattering media. The principle ofGASMAS is that the spectrally sharp gas absorption can be distinguishedfrom the broadband absorption of liquids and solids. This results inthat a small gas absorption signal, (order of 1 in 10 000) can beextracted from light passing through a scattering and absorbing materialdespite transmitting only a minor fraction of the injected light withthe GASMAS method. However, GASMAS was hitherto not known for thepresent field of assessment of packages as defined by embodimentsdescribed herein.

In certain embodiments, the GASMAS technique allows thus for assessmentof packages made of non-transparent, scattering materials that aresurrounding a gas space inside the package or the food product.

It is disclosed a non-intrusive sampling technique, for qualityassurance in the liquid food packaging industry. The GASMAS techniqueopens for analysis of gases inside natural products, such as differentkinds of food where strong light scattering often makes the applicationof conventional gas spectroscopic techniques difficult.

With GASMAS gas located in cavities inside products, such as differentfood items, e.g. meat, bread, fruit and liquids, as well as differentscattering packaging materials, such as plastic and paper, can beanalysed optically for the first time non-invasively. This means thatgas inside headspace of packages that are non-transparent, buttranslucent (i.e. not see through to the eye, but possible for light topenetrate through although not in a straight manner) can be analyzed.

In some embodiments, a simultaneous monitoring of oxygen and watervapour is provided for the headspace of non-transparent, but translucentpackages with a modified atmosphere, using the above described GASMAStechnique.

Due to the scattering of the light in the sample a complication at theevaluation of the absorption signals obtained with the GASMAS method isthe unknown gas interaction path length which the light has experienced.The path length is important in traditional gas absorption spectroscopyfor concentration quantification, as determined by the Beer-Lambertianlaw.

A solution to the conundrum with unknown gas interaction path length isto simultaneously probe a reference gas of known concentration in thesame volume as the measurement gas. This is enabled by using a secondlaser at a wavelength close to the first laser. By forming the ratio ofthe gas absorption signal of the measuring gas and the reference gas aquantity proportional to the concentration of the measuring gas isobtained. Water vapour has been shown to be a feasible reference gas dueto its saturation point at room temperature. In an enclosing with liquidwater present, the concentration of water vapour, only dependent of thetemperature, is known.

Oxygen is of major importance for this application and water vapour ismonitored as a reference gas to enable oxygen concentration evaluation.

It should be emphasized that the term “comprises/comprising” when usedin this specification is taken to specify the presence of statedfeatures, integers, steps or components but does not preclude thepresence or addition of one or more other features, integers, steps,components or groups thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of which embodiments ofthe invention are capable of will be apparent and elucidated from thefollowing description of embodiments of the present invention, referencebeing made to the accompanying drawings, in which

FIG. 1 is a schematic illustration of a gas sensing instrument accordingto an embodiment of the invention.

FIG. 2 a shows a sample of the orange juice packages studied, and FIG. 2b shows an illustration of the detection geometry according to anembodiment of the invention.

FIGS. 3 a-c shows graphs of example signals of oxygen absorption from apackage which is first intact (a), then punctured (b) and lastly flushedwith nitrogen (c).

FIGS. 4 a-c shows diagrams of the equivalent path length (Leq) of oxygenand water vapour as well as the ratio of oxygen and water vapour Leq forthree packages from different expiration dates sets.

FIG. 5 shows diagrams of the ratio of the equivalent path length (Leq)of oxygen and water vapour for the intact packages of the three measuredsets with different expiration dates.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Specific embodiments of the invention will now be described withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art. Theterminology used in the detailed description of the embodimentsillustrated in the accompanying drawings is not intended to be limitingof the invention. In the drawings, like numbers refer to like elements.

In a specific embodiment, a liquid inside a package is orange juice.However, in other examples, embodiments or applications, the liquidinside the package maybe another foodstuff, such as for instance applejuice, cranberry juice, dairy products such as yoghurt, milk, soup,vegetables, soft drinks, wine, prepared foods, poultry or other meatproducts, preserved provisions that traditionally were stored as cannedgoods but thanks to advancements in modern packaging technology arestorable in multilayer packaging material that is translucent asdiscussed herein. In other examples, embodiments or applications, thepackaged material contained in the package may be solid, and/or comprisesolid particles, such as yoghurt with fruit pieces, juice with pulp,etc. In some embodiments or examples, the package is not sealed.

The possibility to assess information about the gas compositionnon-intrusively has been illustrated on a gable top carton package formilk, with a non-modified atmosphere, i.e. air headspace, see Ref. 1,which is incorporated herein by reference in its entirety for allpurposes. In the present disclosure the method is used on series ofcarton packages for fresh orange juice packed in a modified atmosphereof nitrogen. Three series of high quality orange juice packaged inflexible carton packages under modified N2 atmosphere and with differentstorage time, have been measured with aspect of their gas composition.

Three sample sets of orange juice packages, with different expirationdates were analysed. Each set consisted of 20 samples.

Measurement Apparatus Setup

The gas sensing instrument 100 used is depicted in FIG. 1, and consistsof two diode lasers drivers 101, 102, (DFB Nanoplus) monitoring oxygenand water vapour inside food packages 103. The light from the diodelasers (DLs) is brought together and separated into two fibres—one usedto monitor the background (Ref.) and one sent to the sample (Probe),with reference 104 and probe 105 detector respectively. The two diodelasers operate at the wavelengths 760 nm and 935 nm, were the foodpackage and the orange juice are translucent, making the GASMAStechnique suitable. The laser light is guided to the sample 103 viaoptical fibres 106 and a hand held fibre head 108. The scattered lightemerging out from the sample is acquired by a hand held 10×10 mmdetector (Hamamatsu S3590-01) and the generated signal is sampled by acomputer 107. The computer is equipped with a special data acquisitioncard DAQ, making it possible to average the signals. Wavelengthmodulation techniques are used to increase the sensitivity of theinstrument by sinusoidally modulating the wavelength at about 10 kHz andstudying the generated harmonics. Simultaneous detection of water vapourand oxygen is enabled by modulating at different frequencies. In thisembodiment the first overtone (1 f) illustrated on the monitor 109 inFIG. 1, was used for absorption evaluation. Detailed technicaldescription, system performance and data evaluation is presented in Ref.4, which is incorporated herein by reference in its entirety for allpurposes. However, Ref. 4 is on a completely different field oftechnology, namely medical devices for measurement of gas inside thesinus cavities. It is important to note that the light transducer anddetector were hand held and not entirely fixed. In GASMAS completefixation of sample, light delivery and detector often lead todetrimental interference noise. Systematic ways of circumventing thisincludes dithering of laser beam and/or sample.

The gas signal obtained is referenced to a calibration measurement of1000 mm of air, yielding a measure in the unit of mm, referred to as theEquivalent path length, Leq. This quantity is the distance the light hasto travel in ambient air to experience the same gas absorption imprint.The absorption is governed by the Beer-Lambertian law and is dependentof both the species concentration and the distance over which the lightinteracts with the gas. Since the GASMAS technique studies scatteredlight, the gas interaction distance is unknown making it necessary toreference the absorption to a calibration measurement. The quantityobtained, Leq, is thus dependent on both the optical path length and thegas concentration. This means for example that a signal of 20% oxygenwith an interaction distance of 25 mm or an absorption signal of 10%oxygen with an interaction distance of 50 mm gives the same Leq.However, by measuring water vapour, information about the sampling pathcan be obtained. A closed environment with liquid water is saturatedgiving a known water vapour concentration governed only by temperature.Using the equivalent path length, Leq, of water vapour as a measure ofthe interaction distance also for oxygen, results in the ratio of theoxygen and water vapour signals being proportional to the oxygenconcentration. We here rely on the assumption that 760 nm and 935 nmlaser light probe the same volume.

As an alternative to optical gas detection through observation ofdecreased light intensity due to gas absorption, acousto-opticaldetection can be used (See, e.g. Ref. 2, which is incorporated herein byreference in its entirety for all purposes). Then the narrow-band lasersource is periodically shifted from an absorptive wavelength to anon-absorptive one. Collisional deexitation of laser-excited moleculesleads to heat generation, i.e. increased gas pressure. When the laser isperiodically tuned back and forth a periodic gas pressure wave isgenerated which can be detected, e.g. by an acoustic microphone (as a“tone” at the modulation frequency). Frequency- and phase-selectivedetection (lock-in detection) increases the signal-to-noisecharacteristics. Like in the GASMAS method, where light diffuselypassing the gas and then being absorbed for correct laser tuning asdetected by a reduction in light intensity reaching the opticaldetector, photo-acoustic detection integrates the cumulative absorptionexperienced by the diffusing light.

Measurement Experience of Liquid Food Packages

Monitoring of gas inside packages has previously been demonstrated withthe GASMAS technique on bake-off bread, packed minced meat and a gabletop carton of milk, see Ref. 1, which is incorporated herein byreference in its entirety for all purposes. These early measurement wereperformed on single packages in order to illustrate the possibility toassess information about the gas inside sealed packages non-intrusively.The bake-off bread and the meat package were transparent or partlytransparent and had a modified CO2 atmosphere and non-modifiedatmosphere, respectively. Measurements were made non-intrusively throughthe product, while being inside the package. The result illustrated thepossibility to access information about gas seated inside a packagedproduct.

The studied milk was packed in a non-transparent gable top cartonpackage with non-modified atmosphere, i.e. a headspace of air. Theresults demonstrated that it is possible to determine the absorption ofgas inside a headspace non-intrusively despite the fact that the packageappears non-transparent. Both oxygen and water vapour were measured.When the package was perforated the ratio of oxygen and water vapourabsorption signal remained constant. This fact demonstrates that theheadspace oxygen concentration was originally the same as the ambientair. However, an increase in absorption was observed both in the oxygenand water vapour absorption signals following perforation. Thisphenomenon is interpreted as an effective path length increase due tomovement of the sample when the perforation was performed. Theobservation illustrated the need to use simultaneous monitoring of watervapour as a reference in these types of measurements.

Measurements on Packages

In order to analyze the potential of the GASMAS technique as a foodpackaging quality control tool, large sample sets with non-transparentpackages were used to obtain statistical data. Extract of oxygenconcentration information in packages with a modified atmosphereheadspace was investigated.

Three sets of 20 packages of high quality orange juice, packaged inflexible carton portion packages 201 of 250 ml, with a plasticpolyethylene (PE) top and a screw cap opening, were used formeasurements; see FIG. 2 a. The light is injected on the side of theplastic top and detected at the top of the package with the cap removed.Even with the cap removed, the package is still sealed by the mouldedplastic top. The probe 105 may be provided with a thread correspondingto that of the (removed) cap for easy and reliable attachment to thepackage top.

The package 201 consists of a carton based sleeve made of printablepaper coated with layers of polyethylene, and with an injection mouldedplastic top of polyethylene. The headspace of the package is modifiedwith nitrogen, N2, in order to prolong the shelf life of the juice.

The purpose was to identify differences in the gas composition betweenthe three sets with different shelf life. The sets were measured on Jan.26, 2010 and had different expiration dates:

set 1: Oct. 30, 2008,

set 2: Aug. 22, 2009,

set 3: Feb. 23, 2010.

The laser fibre transducer 108 and the light detector 105 were hand heldon the side and at the top of the plastic upper part of the package,respectively; see FIG. 2 b. The cap was removed but the package wasstill intact due to the plastic oblate, the “tamper proof” that needs tobe taken away before consumption. A shielding tube 202 of black paperwas placed around the top of the package top 203 to prevent detection ofleakage light passing from the fibre tip directly to the detector.

Alternatively, the absorption signal may be measured in non-contact moderemote from the sealed package. In an embodiment this may be doneaccording to the principle disclosed in Ref. 3, which is incorporatedherein by reference in its entirety for all purposes. In more detail,measurement of gas in a package may be made by a gas analysis setupusing LIDAR multi-scatter techniques.

Each package was measured three times with repositioning of the laserfibre and detector to verify the reproducibility of the technique. Thepackages were refrigerated during the storage time but placed at roomtemperature one night before the experiment started. A uniform and knowntemperature condition for all packages, to ensure the possibility ofcalibration with water vapour was desired. Each package was weighed inorder to identify any differences between samples and sets. To confirmthe gas absorption signal originated from gas inside the package, andfor absolute oxygen concentration calibration, one sample from each setwas perforated with circular openings of 3 mm and measured with flow ofnitrogen gas and with ambient air in the headspace.

Results

The perforation measurements on one package of each expiration date setshowed that the absorption signal originated solely from the gas insidethe headspace of the package. As nitrogen gas was flushed into theheadspace the oxygen absorption signal basically disappeared. Further,the perforation experiment also verified that the headspace consisted ofa modified atmosphere. Example absorption signals (A) from one packageof the set with expiration date Feb. 23, 2010 are presented in FIG. 3 asfunction of time (t). Oxygen absorption 301 is shown from a packagewhich is first intact (a), then punctured (b) and lastly flushed withnitrogen (c). The black curve is the measured signal and the grey curvea fitted ideal absorption imprint. The intact package gave an oxygenabsorption signal of 34 mm. When puncturing the package the oxygenabsorption signal increased, as the ambient air flowed into the package.Filling the headspace with nitrogen gas resulted in no oxygen signal,i.e. a signal lower than the noise background which for this case wasequivalent to an Leq of 5 mm.

Similar results were obtained for the two other sets with otherexpiration dates when perforated, see FIG. 4 showing diagrams of theequivalent path length (Leq) of oxygen and water vapour as well as theratio of oxygen and water vapour Leq for three packages from differentexpiration dates sets, for package which is first intact (a), thenpunctured (b) and lastly flushed with nitrogen (c). The presented valuesare averaged data of three measurements performed on each packagetogether with the standard deviation. The oxygen absorption signalincreased as the packages were perforated and decreased to the noiselevel as nitrogen was flushed into the headspace. The oxygen absorptionsignal level of the intact packages as well as the perforated packagevaried between the sets. Changes in gas interaction length, due to e.g.,different filling levels, optical properties or measuring geometry,could explain such a variation in oxygen absorption signal. However,when forming the ratio of oxygen and water vapour Leq the discrepanciesbetween the three samples remained for the intact packages, butequalized when the sample packages were perforated and ambient airfilled the headspace. The three studied intact packages of differentexpiration dates can thus be proclaimed to have different amount ofoxygen concentration. As noted, the ratio parameter for the perforatedpackages with ambient air in the headspace all equalized to a similarvalue, corresponds to 21 percent of oxygen concentration. Ourobservation suggests that the ratio of oxygen and water Leq can be usedas an oxygen concentration measure. We here rely on that the watervapour signal is a measure of the probed path through the gas, which ispossible under the condition of saturated humidity. Since small holesare made in the headspace the saturation of the enclosing is pertained.

An increase in water vapour signal was observed as the packages wereperforated and is thought to be an effect of changed gas volume in theheadspace. As the packages were being perforated it was noted that thetop of the cap went from bulking inwards to becoming flat. The decreasein water vapour absorption signal as nitrogen gas is flushed through theheadspace is believed to be an effect of an unsaturated gas volume dueto flow of nitrogen. The ratio between the oxygen and water vapourabsorption signal as an oxygen concentration measure is not feasibleunder such artificial conditions.

The discrepancies in oxygen content, between the intact packages withdifferent expiration dates were further analyzed by studying all the 20samples of each expiration date. The ratio parameter, i.e. the measureof oxygen concentration was monitored, and the results are presented inFIG. 5 showing the ratio of the equivalent path length (Leq) of oxygenand water vapour for the intact packages of the three measured sets withdifferent expiration dates. The presented data are averaged values ofthree measurements performed on each package and is presented to theleft in each column. The average of all 20 measured samples togetherwith corresponding standard deviation is presented to the right in eachcolumn.

No large variation was observed between the samples within one set,whereas a pronounced difference between the sets was obtained. Using theratio value from the perforated packages as 21% oxygen to calculatecorresponding concentration of the intact packages resulted in oxygencontents between 7-15% for the three studied sets. For the newlypurchased packages, where the expiration date had not passed when themeasurement were performed, an oxygen concentration of 10% with astandard variation of 1% between the 20 samples was obtained. For theolder, expired, package sets a lower and higher oxygen concentration wasmeasured, 7±1% and 15±1%, respectively. We note, that the oxygen contentdoes not increase monotonously with storage time. This might indicatevariations in sealing quality of the packaging machine(s). Analternative explanation could be that permeation through the packageand/or through the exchange from product to headspace are in progress todifferent extent. Clear variation between the sets was not only measuredin the ratio but also in the oxygen and water vapour Leq; see Table 1.Different sampling volume, due to scattering and absorption propertiesor filling variation between the sets could explain this behavior.However, the sample sets showed no large variations in weight, 275.4±0.9g, 272.2±1.0 g and 272.4±0.3 g for set 1, set 2 and set 3, respectively.

Table 1 shows data obtained from 20 measured samples from each set withdifferent expiration date. Oxygen and water vapour Leq and their ratiois presented as average±standard deviation. Oxygen concentration iscalculated using the ratio of perforated packages as 21 percent oxygencontent.

TABLE 1 O₂ L_(eq)/H₂O Set Exp. Date O₂ L_(eq) H₂O L_(eq) L_(eq) O₂ conc.1 Oct. 30, 46 ± 3 mm 55 ± 5 mm 0.84 ± 0.06 15 ± 1% 2008 2 Aug. 22, 14 ±1 mm 38 ± 3 mm 0.38 ± 0.05  7 ± 1% 2009 3 Feb. 23, 35 ± 2 mm 59 ± 4 mm0.60 ± 0.05 10 ± 1% 2010

The reproducibility test with three consecutive measures on each sampleshowed no large variation. The ratio parameter varied in average 3%between the measurements. A deviation of the ratio of 3% corresponds toa change in oxygen concentration of 0.45 percentage units (using 15%oxygen as obtained for set 1).

The oxygen concentration may be assessed by measuring the absorptionsignal (optically or photo-acoustically) for an intact package, followedby measurements in the same geometry on the same package for the twocases of a punctured package (yielding an ambient oxygen concentrationof 21 percent) and a package flushed by nitrogen through the hole(s)made by puncturing the package (yielding a zero percent oxygenconcentration). Subsequently a linear interpolation may be applied toderive the proper concentration value. The method then being applicableon intact packages of the same type in the same measurement geometry tonon-intrusively assess the oxygen concentration, without the need ofwater vapour normalization, and corresponding accurate knowledge ofpackage temperature.

In addition, temperature and pressure inside the package may bedetermined based on GASMAS. This makes the assessment in certainembodiments even more accurate and advantageous. For instance a measuredtemperature and pressure inside a package makes it very precise todetermine a water vapour concentration inside the package.

The present disclosure clearly shows that the GASMAS method is highlysuitable for monitoring of gases inside translucent non-transparentpackages. Oxygen is of great interest for the modified atmospherepackaging industry since it is the reduction of oxygen that is soughtfor. An alternative gas to monitor is nitrogen, but this gas does notexhibit any absorption lines that can be studied with diode laserspectroscopy.

A requirement for gas monitoring with the GASMAS technique is that laserlight must be able to travel through the sample, to some extent, andinteract with the gas. In this disclosure about 0.1% of the incidentlaser light, i.e. 1 μW, was transmitted through the package anddetected. It should be noted that the translucency of materials isdifferent and varies with wavelength. For example metal films are nottranslucent at all and liquid water is only translucent below 1400 nm,i.e. in the visible and near infrared regime.

The GASMAS technique is of particular interest for the food packagingindustry since it allows non-intrusive real-time gas monitoring ofnon-transparent packages. The main benefits of using non-intrusivemeasurements are the reduction of sample waste and that no extra costsin terms of extra sensors are added to each individual package.

Another value is the fact that it is possible to analyse the same sampleat different points in time, i.e. over the entire shelf life of theproduct.

The measurements made in the present disclosure on modified atmospherejuice packages, illustrate the possibility to monitor the packed liquidfood as well as the package integrity non-intrusively and over time forshelf-life measurements. This confirms the possibility to use GASMAS oncarton based packages, as indicated in the initial tests made on singlea gable top carton package for milk with ordinary air headspace. Thepresent disclosure augments those results, firstly by showing goodreproducibility and secondly by demonstrating the applicability tomodified atmosphere packaging employing non-transparent packages. Theuse of normalization through water vapour monitoring to gain absoluteoxygen concentration values is also demonstrated.

The results further indicate a potential for non-intrusive qualitycontrol of liquid food products and packages without waste of sample.The possibility to make such measurements non-intrusively indicates afuture potential to introduce food quality measurements in the packagingproduction line as well as in the distribution chain, since thenon-intrusive way of measuring allows for repeatable measures over timeon the same sample. The quality control could certify the tightness ofpackages but also assess possible liquid food deterioration since it ispossible to measure changes in gas composition over time.

A further aspect of food packaging testing is to ascertain that nobodyhas tampered or sabotaged the food package. Actually, recently severalcases of sabotage of food packages have been reported. E.g., glass hasbeen introduced in chicken packages, leading to the need to withdrawhuge amounts of packed product. If someone has tampered with a package,e.g. for introducing contamination, the gas barrier would be broken andsuch a package would exhibit an anomalous gas composition. Even if MAPand CAP techniques have not been applied such tampering would be evidentin the oxygen concentration, since the enclosed product will consumeoxygen by oxidation.

The present invention thus also provides a solution to the non-intrusivemonitoring of the intactness of food packages in the whole supply-chain,from the manufacturer via the distributor(s) to the local grocerystores.

The above technique using MAP or CAP may also be used in otherindustries than food packaging, e.g. to ensure that the product inside asealed package is indeed the original product. This is very useful forindustries having problems with counterfeit and illegally-copied goodssuch as drugs or medicine, clothes, garments, mobile communicationapparatus such as mobile telephones, watches, optical discs such as CDsor DVDs, memory circuits, microprocessors, integrated circuits, ormedical devices.

Instead of using MAP or CAP a unique composition of gas may be used touniquely detect the manufacturer of the goods and/or the product. Thisunique composition is detectable by embodiments of the presentinvention. According to a study of Counterfeiting Intelligence Bureau(GIB) of the International Chamber of Commerce (ICC), counterfeit goodscould make up as much as 5 to 7% of world trade.

Alternatively, a shelf life of packaged goods may be determined based ona gas inside a package, detectable by embodiments of the presentinvention. For instance medical devices may be packaged in a sterileenvironment. For example surgical tools may be positioned in acorrespondingly recessed plastic molding thereof, and packaged in aspecific gas atmosphere for sterility. Shelf life ends when the gasatmosphere no longer is reliably kept by the package, e.g. after six ornine months. Thanks to measuring the gas composition inside the package,the shelf life may be extended when gas inside the sterile package ismeasured and still a sufficient gas atmosphere is detected byembodiments of the present invention.

The simplicity and low cost of a GASMAS instrument makes it a suitabletool for quality control of food packages both in-line and for pointmeasurements. A future “in-line” laser spectroscopy would make itpossible to evaluate non-intrusively if food deterioration has takenplace over time, and whether the oxygen is “consumed” in a tightmodified atmosphere package.

The apparatus 100 in FIG. 1 may be placed in-line within a productmanufacturing chain devised for packaging or products in sealedpackages. The apparatus 100 may thus be placed in connection with forexample a conveyor belt for transportation of food products subsequentto filling and sealing of the food products. The apparatus 100 wouldthen be useable for measurements on each of the food products, or aselection thereof, when transported between filling and sealing and bulkpackaging. The apparatus 100 may be integrated with or standalone withrespect a filling machine and/or packaging machine.

The apparatus 100 may assess the sealed packages without contacting thepackages and instead detect the gas inside the packages from a remotedistance [Ref. 3]. This is advantageous as the speed of detection may beincreased.

Results from measurements shows the feasibility of the GASMAS techniqueas a powerful tool for studying the gas composition as a tool forquality assurance of liquid food products and carton food packaging,performed non-intrusively and over time. The experiments indicate thatthe GASMAS technique can be used for an important problem of securingfood safety through monitoring the quality of liquid food products inmodified or “air tight” packages at different steps in the food supplychain and at different times after packaging. Measurements on highquality orange juice packages with modified atmosphere illustrate thepossibility to non-intrusively monitor the oxygen content and the watervapour content in liquid food packaging over time. In addition, themeasurements indicate a possibility to measure package integrity ortightness non-intrusively based on gas composition measurements.

The present invention has been described above with reference tospecific embodiments. However, other embodiments than the abovedescribed are equally possible within the scope of the invention. Theproduct in the package maybe liquid or solid. Different method stepsthan those described above, performing the method by hardware orsoftware, may be provided within the scope of the invention as definedby the appended claims. The different features and steps of theinvention may be combined in other combinations than those described.The scope of the invention is only limited by the appended patentclaims.

References

-   [1] M. Lewander, Z. G. Guan, L. Persson, A. Olsson and S. Svanberg,    Food Monitoring Based on Diode Laser Gas Spectroscopy, Appl. Phys. B    93, 619 (2008)-   [2] S. Svanberg, Atomic—and Molecular Spectroscopy—Basic Aspects and    Practical Applications, 4th edition (Springer, Heidelberg 2004).-   [3] Z. G. Guan, M. Lewander, R. Grönlund, H. Lundberg, S. Svanberg,    Gas analysis within remote porous target using LIDAR    multi-scattering techniques, Appl. Phys. B 93, 657-663 (2008).-   [4]. Persson, L. Andersson, M. Cassel-Engquist, M. Svanberg, K.    Svanberg, S. Gas monitoring in human sinuses using tunable diode    laser spectroscopy, J. Biomed. Opt. 2007; 12; 054001.

The invention claimed is:
 1. A method for assessment of a sealedpackage, said method comprising: emitting light from a narrow-band lasersource towards said package from outside of said package; determining anabsorption signal of said light scattered in said package, saidabsorption caused by at least one gas in said package when said light isscattered by said package and travels into and out of said sealedpackage, wherein said determining is made outside of said package,whereby said assessment is non-intrusive with regard to said package,and wherein said assessment is based on determining if a deviationexists from a predetermined, expected gas composition and/orconcentration of said at least one gas within said sealed package basedon said measured absorption signal.
 2. Method according to claim 1,wherein said gas is oxygen, and/or wherein said package is translucentfor said light.
 3. Method according to claim 1, wherein determining ofsaid absorption signal comprises: periodically shifting said lasersource between an absorbed and a non-absorbed wavelength of said atleast one gas, detecting a pressure modulation signal generated by saidperiodical shifting with an acoustic detection device so as to obtainphoto-acoustic detection of said absorption signal.
 4. Method accordingto claim 1, wherein determining said deviation comprises: determining afirst concentration of a first gas of said at least one gas, whereinsaid first concentration is determined by, providing said sealed packagein a surrounding atmosphere comprising said first gas having a knownconcentration, measuring a first absorption signal for said first gasthrough said sealed package, puncturing said sealed package to obtain apunctured package, measuring a second absorption signal for said firstgas through said punctured package corresponding to said knownconcentration, flushing said punctured package with a second gasdifferent from said first gas so as to provide a zero concentration ofsaid first gas in said punctured package substantially equal to zero,measuring a third absorption signal for said first gas through saidpunctured package corresponding to said zero concentration, fitting acurve to said second and third absorption signals to provide said firstconcentration corresponding to said first absorption signal.
 5. Methodaccording to claim 1, wherein determining said deviation comprises:determining a first concentration of a first gas of said at least onegas, wherein said first concentration is determined by, measuring afirst absorption signal of water vapour in said sealed package,measuring a second absorption signal of said first gas in said sealedpackage, forming a ratio between said first and second absorptionsignals being proportional to said first concentration so as to providesaid first concentration.
 6. Method according to claim 1, whereindetermining said absorption signal comprises: measuring a first and asecond absorption signal corresponding to a first and a second gas ofsaid at least one gas respectively, forming the ratio between said firstand second absorption signals so as to determine said deviation. 7.Method according to claim 1, wherein determining said absorption signalcomprises having a light transducer and a light detector remote fromsaid sealed package for non-contact assessment of said at least one gas.8. Method according to claim 1, wherein said sealed package is a sealedfood package containing at least partially liquid or solid food, andwherein said sealed package is containing said at least one gas, such asin a headspace and/or inside or integral with a material packaged insidesaid package, and/or wherein said sealed package has been sealed withmodified atmosphere packaging (MAP) and/or controlled atmosphere (CAP)and/or a unique composition of gas.
 9. Method according to claim 1,wherein determining said deviation comprises detecting an absorptionsignal of said at least one gas being different from an expected one,and/or determining a ratio between at least two absorption signals beingdifferent from an expected one, said at least two absorption signalscorresponding to at least two gases in said sealed package.
 10. Methodaccording to claim 1, wherein said assessment comprises determining asealing tightness and/or leakage rate of said sealed package for said atleast one gas over time.
 11. Method according to claim 1, wherein saidassessment comprises determining or excluding a tempering or sabotagingof said sealed package when said deviation is determined or no deviationis determined, respectively.
 12. Method according to claim 11, whereinsaid package is a food package, and said method comprises testing saidfood package to ascertain that nobody has tampered or sabotaged saidsealed package containing food such as juice, soft drinks, wine, milk ormilk products, yogurt, prepared foods, poultry or other meat products.13. Method according to claim 11, wherein said package is a non-foodcontaining package to ensure that the product inside said sealed packageis contains a product originally packed in said package.
 14. Method ofclaim 13, wherein said product is comprised in the list of drugs ormedicine, clothes, mobile telephones, watches, software, CD's and DVD'sor any other sealed product with risk of being counterfeit orillegally-copied.
 15. Method according to claim 1 performed in-linewithin a product manufacturing chain devised for packaging of productsin said sealed packages.
 16. An apparatus for assessment of a sealedpackage comprising: a narrow-band laser source adapted to emit lighttowards said package from outside of said package; a light detectoradapted to measure an absorption signal of said light scattered in saidpackage, said absorption caused by said at least one gas when said lightis scattered and travels in said sealed package, wherein said measuringis made outside of said package, whereby said assessment isnon-intrusive with regard to said package, and wherein said systemfurther includes a control unit adapted to determine if a deviationexists from a predetermined, expected gas composition and/orconcentration of said at least one gas within said sealed package basedon said measured absorption signal.
 17. Apparatus according to claim 16,wherein said apparatus is adapted to perform the method of claim
 1. 18.Apparatus according to claim 16 adapted to be placed in-line within aproduct manufacturing chain devised for packaging of products in saidsealed packages.
 19. Apparatus according to claim 16, wherein said lasersource is adapted to periodically shift between an absorbed and anon-absorbed wavelength of said at least one gas to generate a pressuremodulation signal, said apparatus comprising: an acoustic detectiondevice adapted to detect said pressure modulation signal correspondingto detection of said absorption signal.
 20. Apparatus according to claim16 adapted, wherein said sealed package is a food package, and saidapparatus is arranged for testing said food package to ascertain thatnobody has tampered or sabotaged said sealed package containing foodsuch as juice, soft drinks, wine, milk or milk products, yogurt,prepared foods, poultry or other meat products.
 21. In combination, asealed package and an apparatus according to claim 16, wherein saidpackage contains one or more packaged material comprised in the list ofa foodstuff, drug, medicine, cloth, garment, mobile communicationapparatus, watch, software data carriers, optical discs, memorycircuits, microprocessors, integrated circuits, or medical devices.